Antiblooming imaging apparatus, systems, and methods

ABSTRACT

Apparatus, systems, and methods are described to assist in reducing dark current in an active pixel sensor. In various embodiments, a potential barrier arrangement is configured to block the flow of charge carriers generated outside a photosensitive region. In various embodiments, a potential well-potential barrier arrangement is formed to direct charge carriers away from the photosensitive region during an integration time.

RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.11/605,103, filed Nov. 28, 2006, now U.S. Pat. No. 7,675,093 which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

The information disclosed herein relates generally to imagingtechnology, including image sensors and image processing.

BACKGROUND

Imaging technologies are used in a variety systems and applications, forexample, automobiles, hand-held communications, defense, security andmedical diagnostics. Sensors and other such structures can bemanufactured from semiconductor materials, often at low cost. Moreover,the dimensions of a semiconductor sensor can be scaled to increasedensity and improve device performance. An active pixel sensor (APS) isone such device that can be made with light sensitive semiconductormaterials. Reducing the dimensions of the APS (i.e., scaling to asmaller size) may increase pixel dark current and degrade image quality.Present APS structures may therefore be less desirable for many imagingapplications.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsdescribe substantially similar components throughout the several views.Like numerals having different letter suffixes represent differentinstances of substantially similar components. The drawings illustrategenerally, by way of example but not by way of limitation, variousembodiments discussed in this document.

FIG. 1A-B are a schematics illustrating an APS cell and potentialdiagram according to various embodiments of the invention.

FIG. 2A-C illustrate potential diagrams of an APS cell according tovarious embodiments of the invention.

FIGS. 3A-C illustrate charge related signals for APS cells according toembodiments of the invention.

FIG. 4 illustrates a potential diagram of an APS cell according tovarious embodiments of the invention.

FIG. 5 illustrates a potential diagram of an APS cell according tovarious embodiments of the invention.

FIG. 6 illustrates a potential diagram of an APS cell according tovarious embodiments of the invention.

FIG. 7A-C illustrate imaging data acquired by an array of silicon APScells according to various embodiments of the invention.

FIG. 8 illustrates an imaging apparatus according to various embodimentsof the invention.

FIG. 9 is block diagram of an imaging device according to variousembodiments of the invention.

FIG. 10 illustrates a semiconductor die, according to an embodiment ofthe invention.

FIG. 11 illustrates a circuit module according to various embodiment ofthe invention.

FIG. 12 illustrates a circuit module as an imaging module according tovarious embodiment of the invention.

FIG. 13 is a block diagram illustrating an electronic system accordingto various embodiment of the invention.

FIG. 14 is a block diagram illustrating an optical imaging systemaccording to various embodiments of the invention.

DETAILED DESCRIPTION

An imaging sensor can be made with semiconductor materials such assilicon, germanium, and gallium arsenide. Such semiconductor materialsenable formation of compact and dense arrays of imaging elements in anumber of shapes and sizes. Semiconductor imaging sensors may use theintrinsic properties of the semiconductor material, such as a band gapenergy, to absorb and filter light from an object of interest. In asemiconductor, absorbed light may be converted to an electrical charge.The light absorption properties of semiconductor materials allow devicessuch as imaging sensors to be formed in layers and in variousgeometries. This affords the semiconductor device designer an ability toselect a semiconductor material based on a particular wavelengthapplication as well as for the ability to manipulate the light convertedto electrical charge.

Light is a propagating electromagnetic wave that may be characterized ashaving an associated frequency or wavelength. Light may include aspectrum of wavelengths or a range of frequencies. Light may also becharacterized as a stream of photon particles with an associated energy(or range of energies in the case of multi-wavelength light). Photonenergy and electromagnetic wavelength may be regarded as two differentways to view light. Photon energy (E_(p)) measured in electron volts(eV) and light wavelength (λ) in measured in micrometers (μm) arerelated by E_(p)=1.24/λ. In principle then, all electromagnetic waveshave an associated photon energy. The process of converting absorbedlight (or photons) to charge carriers in a semiconductor is generallyknown as photogeneration. The associated electrical charge is known as aphotogenerated charge. Photogenerated charge carriers are formed aselectron-hole pairs. Photogenerated charge carriers are thereforeelectrons and holes with an attached charge. The efficiency (or rate) ofphotoconversion of absorbed light to charge carriers in a semiconductormaterial is directly related to the intrinsic behavior of its electronicenergy band gap. The rate that charge carriers can be photogenerated ina semiconductor material, generally, depends on the difference betweenthe photon energy of the incident light and the band gap energy of thematerial. In general, light with a photon energy above the band gapenergy of the semiconductor material will be absorbed.

An APS is a semiconductor sensor that uses a photosensitive region toconvert light to electrical charge as generally described above. An APSmay include a floating diffusion region to convert charge accumulated inthe photosensitive region into an output voltage. The photogeneratedcharge may be confined to a region of photosensitive material using aphotogate or pinned photodiode to form a potential well. Increasing thedensity of sensor elements (pixels) in an APS means, generally, reducingthe spacing between photogates. Pixel density may also be increased byreducing the pinned photodiode (or photogate) area and/or the area ofthe floating diffusion region. Reducing the photogate and floatingdiffusion region geometries may increase image noise from extraneouscharge, which is a charge that may be generated in the APS cell fromvarious sources outside the photogate region, including charge producedfrom errant light. The extraneous charge, however small, may be trappedby the floating diffusion region and fill the available electronicstates in that region ever faster as geometries are reduced, or scaledto smaller sizes. Under certain conditions, the extraneous charge mayescape the floating diffusion region and combine with the photogeneratedcharge stored under the photogate or in the pinned photodiode. Once thetwo sets of charges combine, they are not easily separated. Theextraneous charge carriers as an addition to the pool of image-basedphotogenerated charge carriers can be considered a noise related charge.The resulting mix of image and noise related charge may be transmittedto a read circuit as single signal. The combined signal will be greateras a consequence. The transfer of the extraneous charge to thephotosensitive region may therefore be regarded as a form of darkcurrent. The resulting reconstructed electronic image may be of a lowerquality. Many embodiments of the invention address the contribution ofextraneous charge to the photosensitive region that can operate toincrease the dark current of an APS cell.

An APS cell generally operates in one of three possible states. In thefirst state, light absorbed in a photosensitive region generates chargecarriers for a specified time, called the “integration time” herein. Thetotal charge generated is directly proportional to the total number ofphotogenerated carriers. The photogenerated charge stored in aphotosensitive region may be used to reconstruct an electronic image ofan object because the photogeneration rate is also proportional to thearriving photon flux.

In the second state, called the “reset state” herein, charge is removedfrom the floating diffusion region immediately prior to transferring thestored photogenerated charge. The reset state substantially empties thefloating diffusion region of all prior transferred photogeneratedcharge.

In the third state, called the “read-out state” herein, thephotogenerated charge gathered during the integration time in thephotosensitive region may be transferred to the empty floating diffusionregion. The transferred photogenerated charge filling the floatingdiffusion region is therefore representative of a portion of the objectsensed during the integration time. Coupling the floating diffusionregion to a sensing circuit allows the image-based charge to be measured(or read). Arrays of floating diffusion regions coupled tophotosensitive regions may therefore be used to reconstruct arepresentative image of the entire object sensed during the integrationtime. Repeating the above processes of collecting, transferring,reading, and clearing charge allows a moving object to be imaged overtime, providing a time-sequenced series of images.

FIG. 1A is a schematic illustrating an APS cell and potential diagramaccording to various embodiments of the invention. Here the APS cell 140includes a photogate 116 adjacent the photosensitive region 117. The APScell 110 may be formed in a portion of a substrate 112. The substrate112 may be a p-type with a low carrier concentration, or an n-type witha low carrier concentration. The substrate layer 112 may be a materialthat includes any one or more of Si, SiC, Ge, GaAs, InP, GaN, GaP, ZnSe,and ZnS, for example. In some embodiments the substrate comprises asilicon-on-insulator layer. In various embodiments, the substrate may bea silicon-on-sapphire layer. In some embodiments, the substrate 112 mayhave carrier concentration near an intrinsic carrier concentration. Insome embodiments, the APS cell 110 may be formed in a region, such as adoped well, with a conductivity type opposite that of the substrate 112.Doped wells may be used to electrically isolate adjacent APS cells,devices, and circuits further formed in the substrate. The APS cell 110may be formed in a layer 111 on the substrate 112. Layer 111 may havethe same or opposite type conductivity as the substrate 112. Thematerial composition of the layer 111 may be selected according to apreferred crystal lattice spacing or substrate crystal structure. Insome embodiments, the substrate may comprise a single crystalsemiconductor wafer. In some embodiments, the layer 111 may be selectedbased on a band gap energy of a semiconductor material or a wavelengthapplication of interest. Semiconductors that may form the layer 111include any one or more of without limitation, Si, SiGe, SiC, SiGeC, Ge,GaAs, AlAs, AlGaAs, InP, InGaAs, InAs, ZnSe, ZnS, GaN, GaP, AlP, AlGaP,AlAsP, GaAsP, InAsP, AlGaN, AlN, AlInAs, GaInN, GaAsN, GaPN, AlGaAsP,AlGaInAsP, and AlGaInAsPN, In some embodiments, the lattice constant ofthe layer 111 may be the same as the lattice constant of the substrate112. In various embodiments, the layer 111 may be formed fromcombinations of Si, SiGe, SiC, SiGeC, Ge, GaAs, AlAs, AlGaAs, InP,InGaAs, InAs, ZnSe, ZnS, GaN, GaP, AlP, AlGaP, AlAsP, GaAsP, InAsP,AlGaN, AlN, AlInAs, GaInN, GaAsN, GaPN, AlGaAsP, AlGaInAsP, andAlGaInAsPN, for example.

FIG. 1B is a schematic illustrating an APS cell and potential diagramaccording to various embodiments of the invention. Here, the APS cell190 includes a pinned photodiode structure 191 formed in a portion ofthe layer 111B. In some embodiments, the pinned photodiode structure 191may be formed in a portion of the substrate 112B. In some embodiments,the layer 111B is formed from the substrate 112B. In variousembodiments, the layer 111B may be an epitaxial layer.

The pinned photodiode structure 191 may comprise a plurality of dopedlayers 192, 194 and 196 to form a photosensitive region that isfunctionally similar to the photosensitive region 117 of FIG. 1A, aswill be explained below. In some embodiments, the pinned photodiodestructure 191 may be formed with a p-type doped layer 192, an n-typedoped layer 194, and a p-type doped layer 196. In various embodiments,the p-type doped layer 192 is a heavily doped p-type layer. In someembodiments, the pinned photodiode structure 191 may be formed with aportion of the one or more of the doped layers 192, 194 and 196 in thelayer 111B and the substrate 112B. In various embodiments, the layer 196is a doped region of layer 111B. It will be recognized by one ofordinary skill in the art that the p- and n-type impurity concentrationsof the doped layers 192, 194 and 196 can be varied.

Also shown in FIG. 1B is a potential diagram 198 illustrating therespective potentials of the APS cell 190. For simplicity, only the APScell 110 with a photogate 116 is discussed below, but one of ordinaryskill in the art will recognize that the pinned photodiode structure 191of APS cell 190 can be substituted for the photogate 116 of APS cell110, and vice-versa, without substantially effecting the functionalityof the non-photosensitive portions of the APS cell. The portions of theAPS cell 190 that are similar to the APS cell 110, and its respectiveportions of the potential diagram 198 are assigned the same referencenumbers attached to the letter B. One difference between the pinnedphotodiode structure-based APS cell 190 and the photogate-based APS cell110 is the depth of the respective potential wells, 132B and 132. Ingeneral, the depth the potential well 132 with the photogate 116 can beadjusted to be greater than the depth the potential well 132B formed bythe pinned photodiode structure 191. Further, it will be recognized thatoptional layers 125B and 126B, which correspond to optional layers 125and 126, respectively, of FIG. 1A may be formed where front sideillumination is desired.

The APS cell 110 may contain a photosensitive region 117 located underthe photogate 116 (or as discussed, a photosensitive region comprisingthe pinned photodiode structure 191). The dimensions of thephotosensitive region 117, the semiconductor material used, and thenumber of layers may be chosen to provide a desired absorption property.The dimensions of the photosensitive region 117, the semiconductormaterial used, and the number of layers may also be chosen to provide adesired photogeneration rate. In various embodiments, one or moresemiconductor materials may be combined to adjust the absorptionproperties and charge carrier generation rate of an APS cell.

A transfer gate 120 may be formed between the photogate 116 and afloating diffusion region 118. A reset gate 124 may be formed between adrain region 122 and the floating diffusion region 118. The reset gate124 may be formed with the one or more electrical impurities or dopantatoms included in the reset gate region 123. In various embodiments, thereset gate region 123 may include n-type dopant atoms. In someembodiments, the reset gate region 123 may include p-type dopant atoms.The floating diffusion region may be formed as an n-type doped region.The drain region 122 and the floating diffusion region 118 may be formedwith the same type conductivity. In various embodiments, the floatingdiffusion region and the drain region may have a p-type conductivity.

Optional layer 125 may be formed as a filter layer to filter light of adesired wavelength or to filter a spectrum of light wavelengths wherebackside illumination is desired. In some embodiments, layer 125 may beformed as a composite material structure. In some embodiments, layer 125may be formed as a composite of layers. Optional layer 126 is anantireflection layer that may be formed to minimize the reflection ofincident light having one or more wavelengths. In some embodiments,layer 125 and layer 126 may be formed to select the wavelengths of lightthat will be passed through to the substrate layer 112. In variousembodiments, layer 125 and layer 126 may be patterned to allow light toenter one or more regions of the APS cell 110, such as thephotosensitive region 117 under the photogate. In some embodiments, atransparent photogate 116 may be used and the optional layers 125 and/or126 may be formed between the photogate 116 and the photosensitiveregion 117 of the APS cell 110.

In some embodiments, the light may be selected to include a wavelengthin the visible portion of the electromagnetic spectrum. In someembodiments, the light may be selected to include a wavelength in theultraviolet portion of the electromagnetic spectrum. In someembodiments, the light may be selected to include a wavelength in theinfrared portion of the electromagnetic spectrum. In some embodiments,the light may be selected to include wavelengths in the visible,ultraviolet, and infrared portion of the electromagnetic spectrum. Insome embodiments, the light may be selected to include combinations ofwavelengths or bands of wavelengths in the visible, ultraviolet, andinfrared portion of the electromagnetic spectrum. In some embodiments,the light may be selected to include the photopic region of theelectromagnetic spectrum. In some embodiments, the light may be selectedto include a photon energy greater than 1.12 eV.

Also shown in FIG. 1A is an potential diagram 130 illustrating thesurface potential energy along lateral portions of the APS cell 110.Light allowed to propagate through the substrate 112 may be absorbed inthe photosensitive region 117. In some embodiments, the substrate may beused to form the photosensitive region. In various embodiments, thephotosensitive region may comprise the substrate 112. Light absorbed inthe photosensitive region 117 under the photogate 116 may be convertedto charge carriers in the form of electron-hole pairs. Thephotogenerated charge may be stored or otherwise trapped in a potentialwell 132. A voltage may be applied to the photogate 116 to modulate thewidth of the inversion layer 114 and the potential depth of thepotential well 132. The total volume of charge allowed to accumulate inthe potential well 132 can be controlled by adjusting the potentialdepth. For example, for a fixed substrate potential a less positivephotogate voltage may be used to reduce the potential depth (shown as134), thereby lowering the volume of charge that can be stored.Conversely, the amount of photogenerated charge that can be stored maybe increased by applying an increasingly negative photogate voltage.

The charge carriers accumulating in the photosensitive region potentialwell 132 with maximum potential level at 131 may be transferred to thefloating diffusion potential well 136 by a voltage signal applied to thetransfer gate 120 to lower the transfer gate potential barrier 135. Thelower transfer gate potential barrier permits the accumulatedphotogenerated charge carriers to spill over into the floating diffusionregion potential well 136. Once transferred to the potential well 136,the charge carriers lose energy and become trapped (shown, for example,as potential level 138). The floating diffusion region 118 may becoupled at terminal FD to the gate of a source follower (not shown) totransfer a potential of the floating diffusion region 118 out of the APScell 110 where it can be measured. The transfer gate 120, therefore, maybe used to electrically couple the photosensitive region 117 to thefloating diffusion region 118.

The charge carriers in potential well 136 may be transferred or removedto the drain potential well 140 by a positive voltage signal to thereset gate 124 to lower the reset gate potential barrier 137. The lowerreset gate potential barrier allows charge at potential level 138 in thefloating diffusion region potential well to spill over to the drainpotential well 140. The spilled charge may be removed at a potentiallevel 142 to prevent accumulation of charge in the drain potential well.In various embodiments, the drain region 122 may be coupled to a fixedpotential, such as V_(AA-pix). The reset gate 124, therefore, may beused to electrically couple the floating diffusion region 118 to a drainregion 122 that operates as a charge carrier sink (or charge drain).Therefore, the reset gate 124 and the transfer gate 120 may cooperatewith the floating diffusion region 118 using a voltage signal to permitcharge carriers to accumulate in the photosensitive region 117 and moveabout the APS cell using transfer gate region 119 and reset gate region123. In some embodiments, the reset gate 124, transfer gate 120, and thefloating diffusion regions 118 cooperate to direct charge carriers tothe drain region 122. In various embodiments, the reset gate 124,transfer gate 120, and the floating diffusion regions 118 cooperateusing a combination of voltage signals to adjust the barrier heightsduring a read-out interval to direct charge carriers to the floatingdiffusion region 118. In some embodiments, the reset gate 124, thetransfer gate 120, and the floating diffusion region 118 cooperate toprevent charge carriers from entering the region under the photogate116. In various embodiments, the reset gate 124 and the transfer gate120 cooperate with the photogate 116 to reflect charge carriers awayfrom the photosensitive region 117.

In some embodiments, the photosensitive region 117, floating diffusionregion 118, transfer gate region 119, drain region 122, and reset gateregion 123 may be formed from one material. In various embodiments, thephotosensitive region 117, floating diffusion region 118, transfer gateregion 120, drain region 122, and reset gate region 123 may be formedwith combinations of different materials. Various embodiments includeusing combinations of semiconductor materials to provide aphotosensitive region 117, a floating diffusion region 118, a transfergate region 119, a drain region 122, and reset gate region 123 withdifferent light absorption properties. In some embodiments, thephotosensitive region 117, floating diffusion region 118, transfer gateregion 120, drain region 122, and reset gate region 123 may be include aspecified concentration of electrical impurities to adjust at least oneof a threshold voltage, a potential level, and a potential profile. Invarious embodiments, the photosensitive region 117, floating diffusionregion 118, transfer gate region 120, drain region 122, and reset gateregion 123 support one or more dielectric layers (not shown) to adjustat least one of a threshold voltage, a potential level, a potentialenergy profile, and to filter light within a specified wavelength range.

The surface dimensions of the photogate 116 may range between about 0.5μm to about 10 μm. In some embodiments, a photogate region 116 surfacedimension may range between about 1 μm to about 5 μm. The surfacedimensions of floating diffusion region 118 may range between about 0.05μm to about 1 μm. In some embodiments, the floating diffusion region 118may include a dimension ranging between about 0.1 μm to about 0.5 μm.The surface dimensions of the drain region 122 may range between about0.05 μm to about 5 μm. In some embodiments, the drain region 122 mayinclude a surface dimension ranging between about 0.1 μm to about 0.5μm. The transfer gate region 119 dimensions may include a range betweenabout 0.1 μm to about 1 μm. In some embodiments, a transfer gate region120 dimension may be about 0.5 μm. The reset gate region 123 may includedimensions ranging between about 0.1 μm to about 1 μm. In someembodiments, a reset gate region 123 dimension may be about 0.5 μm. Thevertical dimension of the photosensitive region 117 under the photogate116 may range from about 0.05 μm to about 500 μm. In some embodimentsthe photosensitive region 117 may be determined by the thickness of asubstrate, such as a semiconductor wafer. In various embodiments, thedimensions of the photosensitive region 117 may be determined by adimension of a p-doped region, such as p-doped well. The floatingdiffusion region 118 and the drain region 122 may include a dimensionextending into the layer 111 and/or the substrate 112 ranging from about0.1 μm to about 2 μm. In some embodiments, the photogate region 116 maybe formed substantially in the shape of a square, a rectangle, or acircle. In various embodiments, the floating diffusion region 118 and/orthe drain region 122 may include a cross section substantially in theshape of a square, a rectangle, or a circle. In some embodiments, thefloating diffusion region 118, the photogate 116, and the drain region122 may be shaped to cooperate in the transfer of charge carriers. Insome embodiments, a photosensitive region geometry may be configured toreceive light based on the shape of a lens. In various embodiments, thephotosensitive region geometry may be configured to receive light basedon the focal length of a lens. In some embodiments, a photosensitiveregion geometry may be configured to receive light based on a refractiveindex of a lens. In various embodiments, a photosensitive regiongeometry may be configured to receive light based on a refractive indexprofile of a lens.

FIG. 2A illustrates an potential diagram of an APS cell 110 according tovarious embodiments of the invention. Energy diagram 230A illustratesthe electronic state of an APS cell 110 during an integration time. Thedrain potential well 240A may be held at a low potential such thatcharge carriers at potential level 242B lack sufficient energy totraverse the reset gate potential barrier 237A. The drain potential wellmay function as sink for charge carriers to limit the potential of level242A to at or below V_(AA-pix). The floating diffusion region potentialwell 236A contains charge carriers at initial potential level 238A.Initial potential level 238A may exist due to a prior transfer of chargecarriers from photosensitive region potential well 232A. Separating thepotential well 236A from the photosensitive region potential well 232Ais a transfer gate potential barrier 235A that may operate, in part, tocontain the flow of the photogenerated charge carriers at potentiallevel 231A during the integration time.

Light incident on the APS cell 110 may be absorbed in the photosensitiveregion 117 under the photogate 116 and converted to charge carriers.During the integration time, the photogenerated charge carriers may beallowed to accumulate at or below potential level 131. A portion of theincident light may be further absorbed in the floating diffusion region118, the transfer gate region 119, and the reset gate region 123,thereby contributing to the extraneous charge carrier population (notshown) existing outside the photosensitive region 117.

The population of extraneous charge carriers may migrate toward and fallinto the potential well 236A of the floating diffusion region under adrift electric field or by carrier diffusion. As used herein,“extraneous charge carriers” refers to charge carriers outside thephotosensitive region, whether or not photogenerated, falling,migrating, scattering, diffusing, or drifting or otherwise captured inor by the floating diffusion region. The charge in the floatingdiffusion regions 118 can also be created by the dark current generatedby the p-n junction formed from the floating diffusion region 118 andthe surrounding gate regions 119 and 123. The extraneous charge, whetheror not photogenerated or created by the dark current of the floatingdiffusion regions 118, may become trapped in potential well 236A. Thecapacitance associated with the floating diffusion region 118 can besmall, often less than 10 fF. Therefore, accumulating extraneous chargecarriers in potential well 236A may rapidly fill the available potentialwell to potential level 243A. At potential level 243A, the effectivepotential difference between potential well 236A and potential barrier235A may be very small or even non-existent. The lack of a potentialenergy difference allows the charge carriers in the floating diffusionpotential well 236A to escape (shown as 245A) and scatter into thephotosensitive region potential well 232A. Once transferred to potentialwell 232A, the extraneous charge carriers lose energy and mix with thephotogenerated charge accumulating at or below potential level 231A. Thesame potential well that contains the photogenerated charge carriersalso prevents the extraneous charge carriers from scattering back orotherwise returning to the floating diffusion region.

FIG. 2B illustrates an potential diagram of an APS cell 110 according tovarious embodiments of the invention. Energy diagram 230B illustratesthe electronic state of an APS cell 110 during a reset interval. Chargecarriers previously transferred from the potential well 232B to thepotential well 236 across the potential barrier 235B may be removed tothe drain potential well 240B by a positive control voltage signalapplied to the reset gate 124 to lower the height of the potentialbarrier 237B (shown in a non-lowered state as 237A of FIG. 2A) to at,near, or below potential well 236B. The charge carriers in the potentialwell 236B that are transferred to potential well 240B at potential level242B may be removed using voltage V_(AA-pix). This reset operationsubstantially clears the floating diffusion region of all charge inpreparation for a signal read-out operation.

FIG. 2C illustrates an potential diagram of an APS cell 110 according tovarious embodiments of the invention. Energy diagram 230C illustratesthe electronic state of an APS cell 110 during a signal read-outinterval. Here, the reset potential barrier 237C separating potentialwell 236C from potential well 240C is returned to the pre-reset state byremoving the positive control voltage signal from the reset gate 124.The drain potential well 240C may be at a substantially unchangedvoltage level at potential level 242C using V_(AA-pix). After the resetgate potential barrier 237C is substantially at equilibrium, a voltagesignal may be applied to the transfer gate 120 to reduce the height ofthe transfer barrier potential 235C to at, near, or below potential well232C. The loss of the potential barrier 235C allows the charge carriers(shown as 244C) to flow into the potential well 236C, substantiallydraining potential well 232C of the photogenerated charge carriersaccumulated at or below potential level 231C. Further transfer of thephotogenerated charge carriers to the drain potential well 240C isblocked by the potential barrier 237C. The floating diffusion region 118may be further coupled to a circuit, such as a source follower (notshown) or other low noise transistor configuration, to read the voltagethat is proportional to the photogenerated charge. The read charge levelmay be used to form an image bearing a relationship to the incidentlight converted to photogenerated charge carriers in the photosensitiveregion. Therefore, if the charge in potential well 232C includes anextraneous charge, the voltage read may contain excess signal thatcontributes to imaging noise.

FIG. 3A illustrates a timing diagram for an array of APS cells accordingto embodiments of the invention. In the embodiment shown in FIG. 3A, thetime to scan a sequential row of APS cells may be expressed ast _(row)=(t _(sampling) +t _(read-out)×column_width+t _(Horizontal) _(—)_(blank)),where t_(sampling) is the time to sample an accumulated pixel charge inthe floating diffusion region 118 (using a column sampling capacitor),t_(read-out) is the time to readout an entire row of pixel charge storedin the column sampling capacitor, column_width is the number of pixelrows in a specified column, and t_(Horizontal) _(—) _(blank)) is theinterval time that may be included to ensure a proper frame rate. Theframe time is the inverse of the frame rate that may be expressed ast _(frame)=(t _(row)×row_height+t _(Verticle) _(—) _(blank)),where row_height is the number of pixels column in a specified row, andt_(Vertical) _(—) _(blank) is the interval time that may be included toensure a proper frame rate. In some embodiments, the sampling can beperformed during a blanking time interval.

FIG. 3B illustrates charge related signals for an APS cell 110 accordingto embodiments of the invention. Here, the total charge collected in thefloating diffusion region potential well is recorded for six pixels as afunction of integration time (shutter width in rows). The time (t_(row))is proportional to the number of rows of pixels scanned. The pixelpitch, which is the sum of the widths of the photogate 116 and thetransfer gate region 119 along the direction of the scan is 1.7 um. Thesignal for pixels 27-32 is linear out to 1050 rows, at which point thesignal for pixel 31 rapidly increases until reaching saturation at nearrow 2000. Pixel 31 is illustrative of a hot pixel. The rate change inthe signal for pixel 31 can be attributed to charge carriers scatteringfrom the floating diffusion region potential well to the photosensitiveregion potential well containing the accumulating photogenerated chargecarrier (for example, shown as 245A in FIG. 2A). At row 1050, the chargesignal for the adjacent pixels 27-30 and 32 also increases at a morerapid rate. At row 2000, the point where the charge signal for pixel 31has reached saturation, the signals for adjacent pixels 27-30 and 32show further increases in slope. The further slope changes for pixels27-30 and 32 may be associated with the charge carriers for pixel 31scattering into the photosensitive region potential wells of therespective adjacent pixels. This behavior is illustrative of a bloomingcharge.

FIG. 3C illustrates charge related signals for an APS cell 110 accordingto various embodiments of the invention. Here, the total chargecollected in the floating diffusion region potential well is recordedfor pixel 31 (of FIG. 3B) as a function of the shutter width at fourdifferent pixel temperatures. As illustrated, the rate change in thecharge signal for pixel 31 increases earlier and reaches saturationfaster as the pixel temperature increases. The change in rate and theonset of saturation with pixel temperature may be attributed to the rateextraneous charge carriers fill the potential well 136 of the floatingdiffusion region 118. As explained and illustrated above, extraneouscharge carriers accumulating in the floating diffusion potential wellwith an energy at or above the transfer gate potential barrier are ableto scatter or otherwise transfer to the photosensitive region potentialwell (for example, 245A of FIG. 2A). The extraneous charge carriersflowing into the photosensitive region potential well may be consideredas a dark current creating the effect of a hot pixel. The charge relatedto the dark current may be referred to as a blooming charge.

The dark current of a photosensitive region of an APS cell 110 may beapproximated asI _(dark) _(—) _(PD) =Io exp^(q(I) _(dark) _(—) _(FD) ^(T) _(INT)^(CG−φs)/KT),where I_(dark) _(—) _(FD) is the dark current in the floating diffusionregion 118, T_(INT) is the integration time, CG is the conversion gain,KT is a unit of thermal energy, and φs the semiconductor built-inpotential that depends on the Femi level. The relationship between thedark current in the photosensitive region and the integration time maytherefore be expressed asln(I _(dark) _(—) _(PD))∝T _(INT).Although longer integration times, in general, allow more light to bephotogenerated as charge carriers, longer integration times alsoincrease the dark current that includes blooming electrons escaping thefloating diffusion region potential well 136. An anti-blooming featuremay comprise a plurality of potential barriers and a plurality ofpotential wells configured to reduce, inhibit, block or otherwiseprevent charge carriers from entering the photosensitive regionpotential well 132 from the floating diffusion region 136. Reducing,inhibiting, blocking, and otherwise preventing charge carriers fromescaping to the photosensitive region potential well 132 may decreasethe dark current and reduce noise. An anti-blooming feature incorporatedinto the APS cell may limit or even prevent extraneous charge carrierflow, leading to enhanced image quality.

FIG. 4 illustrates an energy band diagram of an APS cell 110 accordingto various embodiments of the invention. Energy band diagram 420illustrates the electronic state an APS cell 110 during an integrationtime using an anti-blooming feature. Here, the height of the resetpotential barrier 437 is reduced by a voltage signal applied to thereset gate 124 during the length of the integration time. The lowerpotential barrier 437 permits charge carriers to flow continuously tothe drain potential well 440. The drain potential well 440 may beconfigured to maintain a substantially constant charge carrier energylevel at 442 using voltage V_(AA-pix) as a charge carrier sink.Latch-type row drivers may be used, for example, to supply the voltagesignals to maintain the on-state condition during the integration time.The height of the reset potential barrier 437 substantially limits theenergy of extraneous charge carriers accumulating in the floatingdiffusion region potential well 436 to potential level 438. The chargecarriers (shown as 444) at potential level 438 are unable to attainenough energy to cross the transfer gate potential barrier 435 into thephotosensitive region potential well 432 to mix with the accumulatingphotogenerated charge carriers at potential level 431. The chargecarriers in potential well 432, therefore, more accurately reflect thecharge carrier population generated using the light from the object tobe imaged. In some embodiments, voltage V_(AA-pix) is a voltage rangingfrom about 1.2V to about 3.5V. In some embodiments, voltage V_(AA-pix)may be 2.8V. In various embodiments, the reset gate voltage signalduring the integration time may range from about 0 to about 3V. In someembodiments, the floating diffusion region voltage signal may range fromabout 1V to about 3V during the integration time. In variousembodiments, the floating diffusion region voltage signal may range fromabout 1.5V to about 2.8V during the integration time. In someembodiments, the transfer gate potential ranges from about 0V to about0.7V during the integration time. In various embodiments, the potentialbarrier 435 and/or the potential barrier 437 may be adjusted to providespecified barrier heights. In some embodiments, the potential barrier435 and the potential barrier 437 may be adjusted to provide a desiredbarrier height differential to direct charge carriers away from thephotosensitive region potential well 432.

FIG. 5 illustrates a potential diagram of an APS cell 110 according tovarious embodiments of the invention. Potential diagram 520 illustratesthe electronic state an APS cell 110 during a signal integration timeusing an anti-blooming feature. Here, the height of the reset potentialbarrier 537 is reduced by a dopant atom profile introduced into thereset gate region 123. In some embodiments, the reset gate potentialbarrier 537 may be formed by adjusting a dopant atom profile in resetgate region 123. A voltage signal may be applied to the reset gate 124to further adjust the height of the reset potential barrier 537. Thelower potential barrier 537 permits the charge carriers to flowcontinuously to the drain potential well 540 during the integrationtime. The drain potential well 540 may be configured to maintain asubstantially constant charge carrier at potential level 542 usingvoltage V_(AA-pix) as a charge carrier sink. The potential barrier 537substantially limits the energy of the extraneous charge carriers in thefloating diffusion region potential well 536 to at or below potentiallevel 538. Extraneous charge carriers attaining energy exceedingpotential level 538 during the integration time are able to flow acrossbarrier 537 to drain potential well 540. Upon falling into the drainpotential well 540, the extraneous charge carriers lack sufficientenergy to return to the potential well 536.

The height of the transfer gate potential barrier 535 may be adjustedusing a dopant atom profile introduced into the transfer gate region119. In various embodiments, the transfer gate potential barrier 535 maybe formed by adjusting a dopant atom profile in the transfer gate region119. In some embodiments, the height of the potential barrier 535 isadjusted to be higher than the potential level at 539 located adjacentto the photogate 116 using a doping profile. In various embodiments, theheight of the potential barrier 535 may be adjusted to be less than thepotential level at 539 using a doping profile. A voltage signal may beapplied to the transfer gate 120 to further adjust the height ofpotential barrier 535. The higher potential of barrier 535 during theintegration time assists the extraneous charge carriers in flowing tothe drain potential well 540. The higher potential of the barrier 535further assists in blocking the transfer of extraneous charge carriersfrom entering the potential well 532. The extraneous charge carriersexceeding the potential level 538 are reflected back to potential well536 or to potential well 540 by the potential barrier 535. The chargecarriers at potential level 538 are unable to attain enough energy tocross the potential barrier 535 into the potential well 532 to mix withthe accumulating photogenerated charge carriers at potential level 531.The charge carriers in potential well 532, therefore, more accuratelyreflect the charge carrier population generated using the light from theobject to be imaged.

In some embodiments, the impurity profiles may be adjusted in the resetgate region 123 and the transfer gate region 119 such that therespective potential barriers are formed to cooperatively reflect anddirect the extraneous charge carriers away from potential well 532. Invarious embodiments, the potential barrier 537 may be further adjustedby a reset gate voltage signal ranging from about 0V to about 2V duringthe integration time. In an embodiment, the reset gate voltage signalmay be about 0.7V during the integration time. In some embodiments, thebarrier potential 535 may be further adjusted by a transfer gate voltagesignal ranging from about −1V to about 2V during the integration time.In an embodiment, the transfer gate voltage signal may be about −0.3Vduring the integration time. In some embodiments, the potential well 536may be adjusted by a voltage applied to the floating diffusion region118 ranging from about 0V to about 3V during the integration time. Invarious embodiments, the potential well 532 may be adjusted by a voltagesignal applied to the photogate 116 ranging from about 0 V to about 3Vduring the integration time. In various embodiments, voltage V_(AA-pix)is a voltage ranging from about 1.2V to about 3.5V. In some embodimentsvoltage V_(AA-pix) may be 2.8V.

FIG. 6 illustrates an potential diagram of an APS cell 110 according tovarious embodiments of the invention. Energy band diagram 620illustrates the electronic state of an APS cell 110 during anintegration time using an anti-blooming feature. Here, the reset gateregion 123 may be processed to include a region of electronic states,such as fast surface states. The transfer gate region 119 may be formedto include substantially bulk semiconductor states. In the region withelectronic states, the leakage current may be greater than in a similarregion with bulk semiconductor states. The electronic states may formin-band electronic states at some energy below the bulk band gap energy.In-band electronic states included in the reset gate region 123 may forma conduction path between the floating diffusion region 118 and thedrain potential well. This may be modeled as a leaky reset gate 124 witha reduced barrier potential 641 in the reset gate potential barrier 637.Extraneous charge carriers in the potential well 636 at or near thereduced gate potential barrier 641 may flow across and fall into thedrain potential well 640. Upon reaching the drain potential well 640,the extraneous charge carriers lose energy and are unable to transferback to the potential well 636. The drain potential well 640 may beconfigured to maintain a substantially constant charge carrier potentiallevel at 642 using voltage V_(AA-pix) as a charge sink. Since theextraneous charge carriers transfer to the drain potential well 640 uponreaching potential level 638, they are unable to attain enough energy tocross the potential barrier 635 well into potential well 632. The chargecarriers at less than or equal to the potential level 631 in potentialwell 632, therefore, more accurately reflect the charge carrierpopulation generated using the light from the object to be imaged.

In some embodiments, an impurity such as a p-type dopant may be used forforming a region including in-band electronic states. In various someembodiments, an n-type dopant may be used for forming a region includingin-band electronic states. In some embodiments, n-type and p-typedopants may be included to form a region including in-band electronicstates. In some embodiments, a dielectric in combination with animpurity profile may be used to form a region including in-bandelectronic states. In various embodiments, an impurity may be includedin a dielectric used to form a reset gate region 123 including in-bandelectronic states.

FIG. 7A illustrates imaging data acquired with an array of silicon APScells according to the various embodiments of the invention. Histogram752A illustrates an image 750A formed using charge carriersphotogenerated in a substantially dark environment. The total darkcurrent for the silicon APS cells is recorded with the image 750A formedat point X. Here, the APS cells are operating as illustrated in FIGS.2A-C. The bright spots (for example, point W) appearing against theotherwise black background as noise are due to the extraneous chargecarriers mixing with the photogenerated carriers in a potential well(for example, 232A) during the integration time. Shown in image 750A isan illustration of a hot pixel effect.

FIG. 7B illustrates imaging data acquired with an array of silicon APScells according to various embodiments of the invention. Histogram 752Billustrates an image 750B formed using charge carriers photogenerated ina substantially dark environment. The total dark current for the siliconAPS cells is recorded with image 750B formed at point Y. Here, the APScells are operating as illustrated in FIG. 4. The histogram 752Bindicates an absence of a dark current tail at above 6000 electrons persecond. At point Y of the histogram, few counts can be detected and fewbright spots can be perceived against the otherwise black background.The lack of bright spots indicates that extraneous charge carriers donot mix with the photogenerated charge carriers in the potential well432 during the integration time. The extraneous charge carriers,therefore, do not contribute to the pixel dark current. Shown in image750B is an illustration of a reduced hot pixel effect using theanti-blooming feature illustrated in FIG. 4 that may improve imagequality.

FIG. 7C illustrates imaging data acquired with an array of silicon APScells according to various embodiments of the invention. Histogram 752Cillustrates an image 750C formed using charge carriers photogenerated ina substantially dark environment. The total dark current for the siliconAPS cells is recorded with image 750C formed at point Z. Here, the APScells are operating as illustrated in FIG. 5 with the reset gate voltageat 0.7V during the integration time. Histogram 752C indicates an absenceof a dark current tail at above 6000 electrons per second At point Z ofthe histogram, few counts can be detected and few bright spots can beperceived against the otherwise black background. The lack of brightspots in the image indicates that extraneous charge carriers do not mixwith the photogenerated charge carriers in the potential well 532 duringthe integration time. The extraneous charge carriers, therefore, do notcontribute to the pixel dark current. Shown in image 750C is anillustration of a reduced hot pixel effect using the anti-bloomingfeature illustrated in FIG. 5 that may improve image quality.

FIG. 8 illustrates an imaging apparatus 800 according to variousembodiments of the invention. The imaging apparatus 800 may include asensor array 810 configured to receive light from an object 860 throughthe lens 815. The light received from the object 860 may be used toreconstruct an image of the object 860 to form a picture. Thereconstructed image of the object 860 may be formed using light havingone or more wavelengths. For example, the image may represent portionsof the object 860 emitting, reflecting, or transmitting one or morecolors, such as red, green, and blue. The object 860 may be illuminatedfrom any angle or side, including back illumination. In some embodimentsthe object 860 may be self illuminating or self emitting such as fromheat emissions. Examples of images include automobiles, automobile taillights, head lights and directional signals and the like, aircraft, seavessels, landscape and terrain, traffic signals and signs, humans,animals, solar matter, pharmaceuticals, bacteria, viruses, geneticmaterial, and other images observable using light. Examples of selfilluminating and self emitting objects include objects having exhaustheat, thermals emissions, black body radiation, ovens, motors,generators, power plants, exothermic reactions such as fermentationprocesses, chemical reactions and concrete curing processes, and otherobjects emitting electromagnetic radiation in the form of heat. Imagingapparatus 800 may be attached to a movable mount or mechanical pivot(not shown) such as a gimbal. The pivot may be coupled to processor (notshown) to specify coordinates, angles and direction of orientation ofthe lens 815, aperture 825, or sensor array 810. The light source 830may be used to illuminate the image. The light source 830 may beoperatively coupled to a controller that is coupled to the sensor array810.

The light source 830 may be used to illuminate an object 860 or toenhance image contrast. The light source 830 may comprise a coherentlight source, an incoherent source such as a broadband light source or anarrow band light source, or a combination of coherent and incoherentlight sources. In some embodiments, the light source 830 may be used toilluminate a portion of an object 860 that is imaged. In variousembodiments, the wavelength of the light source 830 may be selected tomatch an absorption property of the object 860. In some embodiments, animage of object 860 may be formed using light transmitted through theobject. In various embodiments, an image of object 860 may be formedusing light not absorbed by the object 860. Examples of light sourcesinclude, without limitation, a LASER (light amplification by stimulatedemission radiation), a light emitting diode, a black body source such asthe sun, starlight, moonlight, a thermal source, an incandescent lightsource, a halogen light source, and a fluorescent light source. Thesensor array 810 may include a linear array of sensor elements or atwo-dimensional array of sensor elements. The sensor array 810 mayinclude one or more APS cells constructed and operating according tovarious embodiments to the invention, as shown in FIG. 1, 2, 4-6. Invarious embodiments, the sensor elements in a sensor array 810 arepartitioned according to a position within the senor array. In someembodiments, the sensor elements may be partitioned according towavelength. In some embodiments, the lens 815 may comprise a pluralityof lenses. In various embodiments, the lens 815 may comprise an array oflenses. The imaging apparatus 800 may include a sensor array 810configured to receive light through a filter 820 and/or aperture 825.The aperture 825 may be operatively coupled to the sensor array 810using a controller (not shown). In various embodiments, the aperture 825may comprise an electronic aperture configured to reduce the amount oflight received by the sensor array 810. In some embodiments the aperture825 may comprise a shutter. The sensor array 810, the lens 815, thefilter 820, and the aperture 825 may be formed as an integrated module.In some embodiments, combinations of the sensor array 810, the lens 815,the filter 820, and the aperture may be formed as an integrated module.It is to be understood the order of assembly of the lens 815, filter820, and the aperture 825 are shown for conceptual purposes and are notlimited to the positions shown in FIG. 8 and may adjusted according tothe specific application of interest.

FIG. 9 is block diagram of an imaging device 900 according to variousembodiments of the invention. The imaging device 900 may compriseprocessor 925, memory 920, and an imaging module 905. The processor 925may be operatively coupled to memory 920 by a bus 930. Imaging module905 may comprise a sensor array 910, an address decoder 902, row accesscircuitry 904, column access circuitry 906, control circuitry 908,input/output (I/O) circuit 912, and memory 914. The imaging module 905may comprise one or more APS cells (as shown in FIG. 1) operativelycoupled to the row access circuit 904 and to the column access circuit906. The imaging device 900 may be operatively coupled to processor 925or a controller (not shown) to provide control signals to the imagingmodule 905 to access signal content. The imaging module 905 is shown toreceive control signals from the processor 925, such as column and rowaddress enable signals CAS and RAS, respectively. The processor 925 maytransmit address signals to the imaging module 905 specifying the APScell to be read, reset, or allowed to integrate. Control signals such asreset gate signals, transfer gate signals, floating diffusion signals,photogate signals, and signals to null-out extraneous charge carriercontribution to the photogenerated carriers may be provided to theimaging module 905 by the processor 925. The memory device 920 may storedata provided to the processor 925 from the imaging module 905. Memory914 may store data related to an imaged object acquired by the sensorarray 910. It will be appreciated by those of ordinary skill in the artthat additional circuitry and control signals can be provided and thatthe imaging device of FIG. 9 has been simplified to help clarify, andnot obscure, various embodiments of the invention. Any of the sensorarray 910 include an integrated circuit structure and/or elements inaccordance with various embodiments of the invention. For example, thesensor array 910 may be fabricated to include one or more potentialbarriers and potential wells adjusted to store, block, transmit, andremove photogenerated charge carriers and to transmit, block, and removeextraneous charge carriers, as shown in FIGS. 1, 2, 4-6.

It should be understood that the above description of a imaging device900 is intended to provide a general understanding of possible imagingstructures and is not a complete description of all the elements andfeatures of a specific type of imaging device, including APS cells.Further, many embodiments of the invention are equally applicable to anysize and type of imaging module 905 and are not intended to be limitedto the APS cells described above.

FIG. 10 illustrates a semiconductor wafer 1000 according to variousembodiments of the invention. As shown, a semiconductor die 1010 may beproduced from a wafer 1000. The semiconductor die 1010 may beindividually patterned on a substrate layer or wafer 1000 that containscircuitry, or integrated circuit devices, to perform a specificfunction. The semiconductor wafer 1000 may contain a repeated pattern ofsuch semiconductor dies 1010 with the same functionality. Thesemiconductor die 1010 may be packaged in a protective casing (notshown) with leads extending therefrom (not shown), providing access tothe circuitry of the die for unilateral or bilateral communication andcontrol. The semiconductor die 1010 may include an integrated circuitstructure or element in accordance with many of the various embodimentsof the invention, including one or more APS cells, as shown in FIG. 1,2, 4-6.

FIG. 11 illustrates a circuit module 1100 according to variousembodiment of the invention. As shown in FIG. 10, two or moresemiconductor dice 1010 may be combined, with or without a protectivecasing, into a circuit module 1100 to enhance or extend thefunctionality of an individual semiconductor die 1010. The circuitmodule 1100 may comprise a combination of semiconductor dice 1010representing a variety of functions, or a combination of semiconductordice 1010 containing the same functionality. One or more semiconductordice 1010 of circuit module 1100 may contain at least one integratedcircuit structure or element in accordance with embodiments of theinvention, including one or more APS cells, as shown in FIG. 1, 2, 4-6.

Some examples of a circuit module 1100 include imaging modules, memorymodules, sensor modules, device drivers, power modules, communicationmodems, processor modules, and application-specific modules and mayinclude multilayer, multichip modules. The circuit module 1100 may be asubcomponent of a variety of electronic systems, including the system1300 described below. The circuit module 1100 may have a variety ofleads 1110 extending therefrom and coupled to the semiconductor dice1010 providing unilateral or bilateral communication and control.

FIG. 12 illustrates a circuit module as an image module 1200, accordingto various embodiments of the invention. The image module 1200 mayinclude multiple imaging devices 1210 contained on a support 1215. Theimage module 1200 may accept a command signal from an externalcontroller (not shown) on a command link 1220 and provide for data inputand data output on data links 1230. The command link 1220 and data links1230 may be connected to leads 1240 extending from the support 1215. Theleads 1240 are shown for conceptual purposes and are not limited to thepositions shown in FIG. 12. At least one of the imaging devices 1210 maycontain an integrated circuit structure or element in accordance withembodiments of the invention, including one or more APS cells, as shownin FIG. 1, 2, 4-6.

FIG. 13 illustrates a block diagram of an electronic system 1300according to various embodiment of the invention. FIG. 13 shows anelectronic system 1300 containing one or more circuit modules 1100. Theelectronic system 1300 may include a user interface 1310 that provides auser of the electronic system 1300 with some form of control orobservation of the results generated by the electronic system 1300. Someexamples of a user interface 1310 include a keyboard, pointing device,monitor or printer of a personal computer, tuning dial, display, gauge,card reader, keypad, fingerprint scanner, iris scanner, bar codescanners, as well as other human-machine interfaces. Further examples ofsystems 1300 include a camera, a television, a cell phone, a personalcomputer, an automobile, an industrial control system, an aircraft, arobot, an automated control system, a medical diagnostics instrument,analytical instrumentation, and others.

The user interface 1310 may further include access ports provided toelectronic system 1300. Access ports are used to connect an electronicsystem 1300 to the more tangible user interface components previouslyprovided by way of example. One or more of the circuit modules 1100 maycomprise a processor providing some form of manipulation, control ordirection of inputs or outputs to the user interface 1310, or of otherinformation either preprogrammed into or otherwise provided to theelectronic system 1300. As will be apparent from the lists of examplespreviously given, the electronic system 1300 may be associated withcertain mechanical components (not shown) in addition to the circuitmodules 1100 and the user interface 1310. It should be understood thatthe one or more circuit modules 1100 in the electronic system 1300 canbe replaced by a single integrated circuit. Furthermore, the electronicsystem 1300 may be a subcomponent of a larger electronic system. Itshould also be understood by those of ordinary skill in the art, afterreading this disclosure, that at least one of the circuit modules 1100may contain an integrated circuit structure or element in accordancewith embodiments of the invention, including one or more APS cells, asshown in FIG. 1, 2, 4-6.

FIG. 14 illustrates a block diagram of an imaging system 1400, accordingto one embodiment of the invention. An imaging system 1400 may include,an optical imager 1410 and a processor/controller 1420. The imagingsystem 1400 also serves as an example of an electronic system containinganother electronic system, i.e., optical imager 1410, as a subcomponent.The imaging system 1400 optionally contains user interface components,such as a keyboard 1430, a pointing device 1440, a monitor/display 1450,a printer 1460, a memory unit 1470 such as a dynamic random accessmemory, and a bulk storage device 1480. Other components associated withimaging system 1400, such as modems, device driver cards, additionalstorage devices, etc. may also be included. The optical imager 1410, thememory unit 1470, and the processor 1420 may be incorporated on a singleintegrated circuit. Such single package processing units may operate toreduce image processing time and costs. The optical imager 1410 maycontain APS cells, as shown in FIG. 1. In some embodiments, the APScells may contain a structure or element in accordance with embodimentsof the invention, including one or more potential barriers and potentialwells adjusted to store, block, transmit, and remove photogeneratedcharge carriers and to transmit, block, and remove extraneous chargecarriers, as shown in FIGS. 2, 4-6. Examples of imaging system 1400comprising an optical imager 1410 that may incorporate APS cellsaccording to the various embodiments of the invention include automobilemotion sensor systems, security systems, surveillance systems, digitalradiography systems, mammography systems, dental imaging systems,glucose monitoring systems, pulse oximetry systems, digital photographysystems, hand-held communication systems, robotic systems, machinevision systems, aircraft systems, night vision systems, fluorescencesystems, chemiluminescence systems, thermal imaging systems, as well asother systems that sense, detect, or use reflected, transmitted, orabsorbed electromagnetic energy to form an image.

The above Detailed Description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments. These embodiments,which are also referred to herein as “examples,” are described in enoughdetail to enable those skilled in the art to practice the invention. Theembodiments may be combined, other embodiments may be utilized, orstructural, logical, and electrical changes may be made withoutdeparting from the scope of the present invention. The DetailedDescription is, therefore, not to be taken in a limiting sense and thescope of the various embodiments is defined only by the appended claimsand their equivalents.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one. In this document, the term“or” is used to refer to a nonexclusive or, unless otherwise indicated.Furthermore, all publications, patents, and patent documents referred toin this document are incorporated by reference herein in their entirety,as though individually incorporated by reference. In the event ofinconsistent usages between this document and those documents soincorporated by reference, the usage in the incorporated reference(s)should be considered supplementary to that of this document; forirreconcilable inconsistencies, the usage in this document controls.

As used herein, the “integration time” is the time interval (or theperiod of time) the photogenerated charge carriers are allowed toaccumulate in the photosensitive region potential well (e.g., potentialwell 131 of FIG. 1).

It is to be understood that the above description is intended to beillustrative and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. Many other embodiments will be apparent to those of skill inthe art upon reviewing the above description. The scope of the inventionshould, therefore, be determined with reference to the appended claims,along with the full scope of equivalents to which such claims areentitled. In the appended claims, the terms “including” and “in which”are used as the plain-English equivalents of the respective terms“comprising” and “wherein.” Also, in the following claims, the terms“including” and “comprising” are open-ended, that is, a system, device,article, or process that includes elements in addition to those listedafter such a term in a claim are still deemed to fall within the scopeof that claim. Moreover, in the following claims, the terms “first,”“second,” and “third,” etc. are used merely as labels and are notintended to impose numerical requirements on their objects.

The Abstract is provided to comply with 37 C.F.R. §1.72(b), whichrequires that it allow the reader to quickly ascertain the nature of thetechnical disclosure. It is submitted with the understanding that itwill not be used to interpret or limit the scope or meaning of theclaims. Also, in the above Detailed Description, various features may begrouped together to streamline the disclosure. This should not beinterpreted as intending that an unclaimed disclosed feature isessential to any claim. Rather, inventive subject matter may lie in lessthan all features of a particular disclosed embodiment. Thus, thefollowing claims are hereby incorporated into the Detailed Description,with each claim standing on its own as a separate embodiment.

What is claimed is:
 1. A method comprising: converting photons toelectrons in a first potential energy region at a predetermined rate;storing the electrons in the first potential energy region during anintegration time; and adjusting a first barrier energy relative to atleast one of a second barrier energy or a third barrier energy to reducetransfer of electrons from a second potential energy region to the firstpotential energy region during the integration time by permittingelectron transfer from the second potential energy region to flow in adirection away from the first potential energy region, the secondpotential energy region being in a path of reading out, after theintegration time, the electrons stored in the first potential energyregion.
 2. The method of claim 1, wherein converting photons toelectrons includes converting photons having an energy range associatedwith a predetermined frequency band.
 3. The method of claim 1, whereinconverting photons to electrons includes converting photons associatedwith at least one of automobile light, sunlight, starlight, moonlight,or thermal energy.
 4. The method of claim 1, wherein the convertingphotons to electrons includes selectively converting photons using atleast one of a filter, a semiconductor band gap, or a reflective surfacecoating.
 5. The method of claim 1, wherein storing includes accumulatingelectrons during the integration time using at least one of a lens or ashutter.
 6. The method of claim 1, wherein storing includes accumulatingelectrons using a dopant atom adjusted barrier potential.
 7. The methodof claim 1, wherein storing includes accumulating electrons generatedfrom photons associated with at least one of a visible wavelength, anultraviolet wavelength, or an infrared wavelength.
 8. The method ofclaim 1, wherein adjusting a first barrier energy relative to at leastone of a second barrier energy or a third barrier energy includesapplying one of a first voltage, a second voltage, or a third voltage.9. The method of claim 1, wherein adjusting a first barrier energyrelative to at least one of a second barrier energy or a third barrierenergy includes using a dopant atom profile.
 10. A method comprising:converting photons to electrons in a first potential energy region in aphotosensitive region at a predetermined rate; storing the electrons inthe first potential energy region during an integration time prior totransferring the electrons to a diffusion region for an associatedread-out operation; and adjusting a barrier energy between the diffusionregion and a reset gate region directly adjacent the diffusion region toreduce the transfer of electrons from a second potential energy regionto the first potential energy region during the integration time, thesecond potential energy region corresponding to the diffusion region.11. The method of claim 10, wherein the method includes applying apotential, during the integration time, to a drain associated with thereset gate region, the drain providing a charge carrier sink.
 12. Themethod of claim 10, wherein the method includes using a photosensitiveregion in which the first potential energy region includes a potentialwell with two ends, one end being adjacent a transfer gate regioncoupled to the diffusion region, the one end being adjacent a transfergate region having a higher potential barrier height than the otherbased on a doping profile in the transfer gate region.
 13. The method ofclaim 10, wherein the method includes using a reset gate region havingin-band electronic states to form a conduction path between thediffusion region and a drain potential well.
 14. The method of claim 10,wherein the photosensitive region includes a photodiode structure. 15.The method of claim 10, wherein the photosensitive region is locatedbelow a photogate.
 16. A method comprising: converting photons toelectrons in a first potential energy region in a photosensitive regionat a predetermined rate; storing the electrons in the first potentialenergy region during an integration time prior to transferring theelectrons to a diffusion region for an associated read-out operation;and adjusting a barrier energy between the photosensitive region and atransfer gate region directly adjacent the photosensitive regionrelative to one or more barrier energies associated with a reset gateregion directly adjacent the diffusion region, the adjustment to reducethe transfer of electrons from a second potential energy region to thefirst potential energy region during the integration time, the secondpotential energy region corresponding to the diffusion region.
 17. Themethod of claim 16, wherein the method includes applying, during theintegration time, a voltage to a gate above and corresponding to thereset gate region to permit charge carriers in the diffusion region toflow to a charge carrier sink away from the photosensitive region. 18.The method of claim 16, wherein the method includes using a transfergate region and a reset gate region each having a doping profileselected to enhance electron flow from the diffusion region to a drainadjacent to and corresponding to reset gate region while reducing thetransfer of electrons to the photosensitive region during theintegration time.
 19. The method of claim 16, wherein the method includereceiving light at the photosensitive region from backside illuminationof a substrate in which the photosensitive region is disposed in thesubstrate opposite the backside.
 20. The method of claim 19, whereinreceiving light at the photosensitive region from backside illuminationof a substrate includes receiving the light resulting from opticalfiltering at the backside.